1. Field of the Invention
The present invention relates to an ink-jet recording method for recording input data such as characters, images, and pictures on a recording medium. Also, the present invention relates to an ink-jet recording apparatus using an ink-jet recording head for performing such method. Further, the present invention relates to an information-processing system comprising the ink-jet recording apparatus as an output device, such as a copying machine, a facsimile, a printer, a word processor, and a personal computer.
Here, it should be construed that a term xe2x80x9crecordingxe2x80x9d involves a technical concept of applying ink to all kinds of ink receiving articles such as cloth, thread, paper, and sheet-like materials each adapted to receive ink from the ink-jet recording head (in the form of printing, image forming, dyeing or the like), and that the present invention can be applied not only to a field of information processing but also to a various kind of industrial field (for example, an apparel industry) by using the ink receiving article mentioned above.
2. Description of the Related Art
Many proposals have been hitherto made with respect to a recording apparatus for performing a recording operation on a recording medium such as paper, cloth, plastic sheet, and OHP sheet (hereinafter referred to generally as a recording paper) with the aid of a recording head mounted on the recording apparatus so as to operate in accordance with various kinds of recording methods such as a wire dot recording method, a heat susceptible recording method, a thermal transfer recording method, and an ink-jet recording method.
Among the aforementioned recording methods, the ink-jet recording method belongs to a no-impact recording method of ejecting ink from an ink-jet recording head so as to allow the ink to adhere directly to a recording paper, and it is generally classified into two types, one of them being a continuous type (inclusive of an electric charge particle controlling type and a spraying type) and the other one being an on-demand type (inclusive of a piezo type, a sparking type and a bubble jet type).
The continuous type ink-jet recording method is practiced such that ink is continuously ejected to a recording paper from an ink-jet recording head and electric charge is applied only to necessary ink droplets among a number of ejected ink droplets. Thus, the electrically charged ink droplets adhere to the recording paper but the remaining ones are uselessly wasted.
On the contrary, the on-demand type ink-jet recording method is practiced such that ink is ejected from an ink-jet recording head only when ink ejection is required for performing a recording operation. Thus, the on-demand type process does not cause the trouble of uselessly ejecting ink from the ink-jet recording head to contaminate the interior of a recording apparatus with ink droplets. In addition, with respect to the on-demand type ink-jet recording method, each recording operation is controlled so as to perform repeatedly starting and stopping ink ejection and it can be achieved at a high speed by increasing the number of ink ejecting nozzles.
Many of recording apparatuses commercially sold at present are constructed in accordance with the on-demand type ink-jet recording method. Since a recording apparatus including an ink-jet recording head of the foregoing type makes it possible to perform a recording operation not only at a high density but also at a high speed, it is utilized and commercialized as outputting means for an information processing system, e.g., a printer serving as an output terminal unit for a copying machine, a facsimile, an electronic typewriter, a word processor, a work station or the like or a handy or portable type printer to be equipped in a personal computer, a host computer, an optical disc unit, a video unit or the like. In the circumstances as mentioned above, an ink-jet recording apparatus is constructed in such a manner as to match with a function and a type of practical use inherent to each of the aforementioned units.
In general, the ink-jet recording apparatus includes a carriage having recording means (ink-jet recording head) and an ink tank mounted thereon, conveying means for conveying a recording paper and controlling means for controlling the carriage and the conveying means. As ink is ejected from a plurality of ink ejecting nozzles on the ink-jet recording head in the form of ink droplets, serial scanning is performed in the direction (main scanning direction) orienting at a right angle relative to the conveying direction of the recording paper (auxiliary scanning direction). Subsequently, the recording paper is intermittently conveyed by a quantity equal to a recording width during the inoperative state of the ink-jet recording apparatus having no recording operation performed therewith. In response to a recording signal, the ink-jet recording apparatus performs a recording operation by ejecting ink onto the recording paper.
On the other hand, an ink-jet recording method to be practiced in association with the ink-jet recording apparatus is widely used as a quiet recording method capable of being employed at a low running cost. Since a plurality of ink ejecting nozzles are disposed along a straight line extending in the auxiliary scanning direction on the ink-jet recording head, each recording operation is achieved with a width corresponding to the number of ink ejecting nozzles every time the ink-jet recording head performs scanning over the recording paper. Consequently, the ink-jet recording method makes it possible to achieve a recording apparatus at a high speed.
In the case of a color ink-jet recording apparatus for printing in two or more colors, a multicolor image is formed by allowing ink droplets to overlap one above another on a recording paper by ejecting inks of several colors from a plurality of color ink-jet recording heads each including a plurality of ink ejecting nozzles. Generally, in the case that a color recording operation is performed with the color ink-jet recording apparatus, three or four ink-jet recording heads and three or four ink cartridges corresponding to three primary colors composed of yellow (Y), magenta (M) and cyan (C) or four colors composed of three primary colors and black (B). Lately, a color ink-jet recording apparatus having three or four kinds of color ink-jet recording heads mounted thereon so as to enable an image to be formed with full color has been put in practical use.
In addition, the foregoing type of color ink-jet recording apparatus can be constructed in such a manner as to enable an image to be comparatively easily recorded on a recording medium with a size of xe2x80x9cA-1xe2x80x9d. Concretely, a color ink-jet recording apparatus electrically connected to a reader adapted to read an A-1 sized original of multicolor image so as to allow the original to be recorded on a recording paper, e.g., a plotter serving as a CAD output printer has been commercialized. On the other hand, it is practically required that the color ink-jet recording apparatus can be used in a variety of fashions, and lately, requests have been increasingly raised from users for providing a color ink-jet recording apparatus capable of recording various kinds of information such as characters, graphs, pictures, and figures on an OHP film in order to visually project the information on a screen for the presentation in a conference or lecture. To satisfactorily meet these requests, a number of development works have been conducted to commercialize an ink-jet recording apparatus capable of performing an optimum recording operation regardless of the kind of recording paper employed when a recording medium having properties of absorbing ink is selected as desired.
In addition, many requests have been raised from wide industrial fields (e.g., apparel industry) for providing an ink-jet recording apparatus of the foregoing type serving as excellent recording means for recording a higher quality of image on a recording medium.
Next, description will be made below with respect to an ink-jet recording head (hereinafter referred to simply as a recording head) to be mounted on an ink-jet recording apparatus.
Energy generating means disposed in the recording head for generating energy required for ejecting ink from the recording head is exemplified by an electromechanical transducer (such as a piezo element) and an electrothermal transducer including a heat generating resistor for the purpose of heating liquid.
With respect to a recording head of the type (i.e., a so-called bubble jet type) of ejecting liquid therefrom by utilizing thermal energy, i.e., by utilizing a phenomenon of film boiling (so-called bubble jet type recording head), since a plurality of liquid ejecting nozzles can be disposed at a high density, it is possible to perform a recording operation with a high level of resolution.
To facilitate understanding of the present invention, a conventional ink-jet recording head and a conventional ink-jet recording apparatus having the conventional ink-jet recording head mounted thereon will be described below with reference to FIG. 1 and FIG. 2.
FIG. 1 shows by way of schematic perspective sectional view the structure of an ink-jet recording head to be mounted on an ink-jet recording apparatus.
Reference numeral 91 designates a ceiling plate. A plurality of grooves 93 each serving as a nozzle for allowing ink to flow therethrough, a groove 94 communicated with the grooves 93 to serve as a common liquid chamber, and an ink feeding port 95 for feeding ink to the common liquid chamber therethrough are formed on the ceiling plate 1. Reference numeral 92 designates a base plate which is formed integral with a plurality of electrothermal transducers 96 serving corresponding to respective ink ejecting nozzles and a plurality of electrodes 97 for feeding electricity to the respective electrothermal transducers 96 by employing a film forming technology. A plurality of ink ejecting ports 98 (orifices) for ejecting ink therefrom are formed in combination of the ceiling plate 91 with the base plate 92.
The recording head constructed in the manner as described above is integrated with an ink tank for feeding ink thereto through the ink feeding port 95 to constitute an ink-jet cartridge.
FIG. 2 shows by way of schematic perspective view the structure of an ink-jet recording apparatus having the ink-jet recording head shown in FIG. 1 mounted thereon.
In the drawing, reference numeral 120 designates an ink-jet recording head (recording head) for an ink-jet cartridge IJC which includes a group of ink ejecting nozzles facing to the recording surface of a recording paper conveyed onto a platen 124. Reference numeral 116 designates a carriage HC for holding the recording head 120 thereon. The carriage HC is fastened to part of a driving belt 118 which transmits thereto the driving force generated by a driving motor 117. The carriage HC can reciprocably be displaced across the whole width of the recording paper with the aid of two guide shafts 119A and 119B extending in parallel with each other. As data are received by the recording head 120, images are recorded on the recording paper corresponding to the received data during the reciprocable displacement of the recording head 120. The recording paper is conveyed by a predetermined distance on completion of each main scanning, and subsequently, auxiliary scanning is performed with the recording head 120.
Reference numeral 126 designates a head recovering unit which is arranged at the position facing to one end of the path of displacement of the recording head 120, e.g., the position located opposite to a home position of the recording head 120. As the driving force generated by a motor 122 is transmitted via a power transmitting mechanism 123, the head recovering unit 126 is activated, causing the recording head 120 to be capped with a cap portion 126A. Subsequently, ink is sucked (to attain suction recovery) by driving adequate sucking means (e.g., suction pump) disposed in the head recovering unit 126 in operative association with the capping portion 126A of the head recovering unit 126, whereby ink located in the ink ejecting ports of the recording head 120 with increased viscosity is forcibly discharged from the ink ejecting ports, resulting in the recording head 120 being subjected to ink discharge recovering treatment. In addition, the recording head 120 is protected from an occurrence of malfunctions by allowing the recording head 120 to be capped with the capping portion 126A after completion of each recording operation. Such ink discharge recovering treatment as mentioned above is executed when a power source is turned on or when the recording head 120 is replaced with a new one or when no recording operation is performed for a period of time longer than a predetermined one.
Reference numeral 131 designates a blade molded of a silicone rubber. The blade 131 is disposed on the right-hand side surface of the head recovering unit 126 to serve as a wiping member while it is held by a blade holding member 131A in the cantilever-like fashion. Similar to the head recovering unit 126, the blade 131 is actuated by the motor 122 and the power transmitting mechanism 123 until it is engaged with an ink ejecting plane of the recording head 120. The blade 131 is projected in the path of displacement of the recording head 120 at a certain adequate timing during each recording operation performed by the recording head 120 or after the ink discharge recovering treatment conducted by the head recovering unit 126, whereby dew, moisture or dust particle on the ink ejecting plane of the recording head 120 is wiped off by the blade 131 as the recording head 120 is displaced in the leftward/rightward direction.
Next, a plurality of steps of forming ink droplets in accordance with the bubble jet recording method to be practiced by the recording head constructed in that way will be described below.
Specifically, when a heat generating resistance (heater) is heated to reach a predetermined elevated temperature, a film-like gas bubble is formed in such a manner as to cover the heater surface with the gas bubble. Since an intensity of pressure in the gas bubble is very high, ink in each nozzle is squeezed outside of a nozzle. Then, ink is displaced not only outside of the nozzle but also toward the common liquid chamber located opposite to the nozzle under the influence of the inertia force induced by the squeezing of ink. As ink is increasingly displaced, the pressure in the gas bubble becomes negative. Since the resistance against the flowing of ink in the liquid flow passage is additionally applied to the negative pressure, the speed of ink displacement in the nozzle is reduced. On the other hand, ink discharged outside of a nozzle (orifice) is displaced at a speed higher than that of ink in the nozzle, causing a necked part to appear on the gas bubble attributable to the balance established among the inertia force, the resistance against the flowing of ink through the liquid flow passage, the contraction of the gas bubble and the surface tension of ink. A part of ink in the nozzle is separated away from the nozzle in the presence of the necked part of the gas bubble, and thereafter, it is transformed into an ink droplet. Subsequently, as the gas bubble is contracted, ink is fed to the nozzle from the common liquid chamber by the capillary force. At this time, the recording head is ready to receive a next pulse.
In such manner, the recording head having a plurality of electrothermal transducers used as energy generating means assures that in response to a pulse-like signal induced by a driving current, a gas bubble can be generated in ink in the liquid passage in the one-to-one relationship, and moreover, the gas bubble can instantaneously and adequately be grown and contracted, whereby an ink droplet can be discharged from the recording head especially with excellent responsiveness. In addition, the recording head can easily be designed and constructed with remarkably reduced dimensions, and since advantages derived from the integral circuit technology and the micro-machining technology remarkably advanced and improved in reliability in recent years can sufficiently be utilized for the recording head, a plurality of recording heads can easily be mounted on an ink-jet recording apparatus while each recording head is fabricated at an inexpensive cost.
Next, the method of determining a gray level based on the conventional ink-jet recording apparatus constructed in the above-described manner is exemplified by a method of allowing one pixel representing an image signal to correspond to one pixel representing binary recording and then expressing a gray level by binarizing the thus corresponding pixel with reference to a predetermined threshold value (dither method), a method of changing a magnitude of each dot by forming a composite liquid droplet composed of a plurality of liquid droplets and then shooting it onto a recording medium as disclosed in official gazettes of Japanese Patent Application Laying-open Nos. 207256/1984, 160654/1982 and 53052/1988 (liquid droplet modulating method) and a method of forming one bit by shooting a plurality of liquid droplets onto a recording medium at a same location on the latter to form one dot therewith and then determining a gray level depending on the number of liquid droplets shot onto the recording medium as disclosed in an official gazette of Japanese Patent Application Laying-open No. 53052/1988 (multi-droplet method). Among them, the dither method has a drawback that a level of image resolution is increasingly reduced, and the liquid droplet modulating method has a drawback that a wide gray level width is hardly determined within the practical range defined by a distance between a recording apparatus and a recording paper. On the contrary, the multi-droplet method has an excellent advantage that each recording operation can be achieved not only at a high gray level but also with a high level of resolution by selectively using an ink-jet recording head adapted to eject a number of small liquid droplets therefrom.
Generally, a period of time of several hundred milliseconds are taken until ink penetrates into a recording medium after liquid droplets are shot onto the recording medium. When a preceding liquid droplet is shot onto the recording medium, a semisphere liquid droplet is formed on the recording medium. Thus, as subsequent liquid droplets are successively shot onto the preceding liquid droplet on the recording medium in the overlapping state, a larger semispherical liquid droplet can be formed on the recording medium, and it is possible to control a size of each pixel by changing the number of liquid droplets overlapping one above another.
Although it is anticipated that a recording speed is undesirably reduced when the number of liquid droplets to overlap one above another is increased to attain a wide gray level width, this problem can be solved by combining the aforementioned liquid droplet modulating method with a method of shooting liquid droplets each having a different volume ejected from different nozzles on a recording medium in the overlapping state for a very short period of time with the aid of an ink-jet recording head as disclosed in an official gazette of Japanese Patent Application Publication No. 502261/1988.
FIG. 3 and FIG. 4 illustratively show a series of steps of forming a pixel in accordance with the multi-drop process, respectively. This process is intended to form one pixel by shooting a plurality of liquid droplets on a recording medium at the substantially same location of the latter in the overlapping state. In this case, the pixel formed by one liquid droplet may be taken as one pixel. In FIG. 4, a pixel frequency fo determines a minimum distance between adjacent pixels on the recording medium as measured in the main scanning direction of the ink-jet recording head. In addition, a liquid droplet ejection frequency fo determines the number of ink droplets shot onto the recording paper at the substantially same location on the latter.
Referring to FIG. 3 and FIG. 4, an ejection signal P21 is applied to ejecting means disposed in a nozzle of the ink-jet recording head to eject a liquid droplet D1 from the nozzle. After a period of 1/f elapses, a liquid droplet D2 is ejected on a pixel 101 formed with the liquid droplet D1 on a recording medium 103 in response to a selective ejection signal P22 in such a manner that at least a part of the liquid droplet D2 overlaps on the pixel 101. Similarly, in response to ejection signals P23 and P24, liquid droplets D3 and D4 are ejected from the nozzle, causing the formation of a pixel 102 to be completed. A size of each pixel on the recording medium can be changed to another one in the course of the aforementioned steps depending on whether the ejection signals P21, P22, P23 and P24 are applied to the ejecting means or not. In the case that a different pixel is formed adjacent to the pixel 102, it is sufficient that an ejection signal P21xe2x80x2 is applied to the ejecting means after a period of 1/fo counted from the application of the ejection signal P21 to the ejecting means elapses.
Granularity of a high light part on a multi-valued image can be noted as a factor having significant effect on a quality of multi-valued image. Especially, in the case that a pixel formed with one liquid droplet has a large size, the foregoing granularity can remarkably visually be recognized by anyone, resulting in a quality of image being deteriorated. To assure that the deterioration of the quality of image can be prevented by reducing an extent of granularity, it is necessary that each pixel is formed with smaller liquid droplets. For example, an examination conducted by the inventor of the present invention reveals that when an image colored with black is observed at a location remote from the image by a distance of about 25 cm or more, the quality of image is not greatly deteriorated irrespective of the observer""s sense affected by the granularity of image, as long as an average diameter of each pixel on the recording medium remains within the range of 5 to 50 xcexcm. In addition, when each pixel has an average diameter of 30 xcexcm or less, the deterioration of the quality of image is negligibly small.
However, if the high light part of an image on the recording medium is formed only with liquid droplets each having such a size that the granularity of image is not remarkably recognized by anyone, one pixel is formed with a larger number of liquid droplets when a high density part on an image is formed with liquid droplets. For example, when an image is formed with liquid droplets each having a volume of 10 pl, the granularity of a high light part on the image is less visually recognized than the case that liquid droplets each having a volume of 20 pl are used for forming the image. However, to assure that an image is formed at a substantially same density, the number of liquid droplets as many as two times of the number of liquid droplets each having a volume of 10 pl are required. In addition, to maintain an image output time in the case that liquid droplets each having a volume of 20 pl are used, liquid droplets each having a volume of 10 pl should be ejected from the ink-jet recording head at a frequency as high as about two times. Generally, when a volume of each liquid droplet ejected from the ink-jet recording head is reduced to a level of 10 pl or less, it is not easy to substantially improve a time to be taken until an ink meniscus in each nozzle is restored to the position prior to ink ejection after ink is ejected from the nozzle (hereinafter referred to as a refill time), merely by modifying the structure of the nozzle to some extent. In the case that a liquid droplet is ejected from each nozzle before the meniscus is restored to the foregoing position, it is difficult to maintain stable ink ejection.
To cope with the foregoing problems, it is thinkable that a measure is selectively taken such that a multi-valued image having a high quality is obtained by using an ink-jet recording head adapted to successively eject a number of small liquid droplets therefrom to form a pixel in such a manner that granularity of the pixel is not clearly recognized by anyone although an image output speed is slow to some extent. With this ink-jet recording head constructed in that way, however, there sometimes arises an occasion that viscosity of ink remaining in each nozzle is increased due to evaporation of volatile components in ink with the result that incorrect ink ejection such as deformation of a recorded image, failure of ink ejection or the like occurs due to the reduction of a liquid droplet ejection speed. This tendency is remarkably recognized more and more in the case that an ink-jet recording head having a small nozzle size and a small orifice area is employed for an ink-jet recording apparatus in order to obtain small liquid droplets. Therefore, to assure that a high quality of multi-valued image is obtained by successively ejecting a number of small liquid droplets from the ink-jet recording head in such a manner that granularity of a pixel is not visually clearly recognized by anyone, it is inevitable to take a measure against a mode of incorrect ink ejection.
To solve the foregoing problem, a proposal has been made with respect to a so-called preliminary ink ejection sequence for allowing liquid droplets unusable for each recording operation to be ejected from an ink-jet recording head during the standby state or during the recording operation. For example, the preliminary ejection sequence is exemplified by a method of executing preliminary ink ejection by displacing the ink-jet recording head to a predetermined position located outside of the recording range (as disclosed in an official gazette of Japanese Patent Application Laying-open No. 9928/1979) and a method of executing preliminary dispersive ink ejection for a recording medium after each elapse of a predetermined time period (as disclosed in an official gazette of Japanese Patent Application Laying-open No. 139269/1980). As a concrete method of executing preliminary ejection with a thermal ink-jet recording head, the applicant common to the present invention has already proposed a method of executing preliminary heating with the aid of a heater at the same time as preliminary ink ejection is executed (as disclosed in an official gazette of Japanese Patent Application Laying-open No. 146552/1986) and a method of executing preliminary ink ejection with a larger quantity of energy than that required during each recording operation (as disclosed in an official gazette of Japanese Patent Application Laying-open No. 146556/1986)
However, when each of the prior methods as disclosed in official gazettes of Japanese Patent Application Laying-open Nos. 9928/1979, 146552/1986 and 146556/1986 is employed for an ink-jet recording head, an image output speed is additionally reduced as the ink-jet recording head is displaced to a predetermined position located outside of the recording range. For this reason, it can not be concluded that each of the aforementioned prior methods is a preferable method. Generally, about 10 to 1000 liquid droplets are ejected from each nozzle every time preliminary ink ejection is executed in order to obtain desired advantageous effects. However, in the case that the method as disclosed in an official gazette of Japanese Patent Application Laying-open No. 139269/1980 is employed for executing preliminary dispersive ink ejection, there appears a drawback that granularity on an image is not visually recognized at the high light part of the image but it is liable to be remarkably visually recognized as color contamination.
The present invention has been made in consideration of the aforementioned problems to be solved.
An object of the present invention is to provide an ink-jet recording method which assures that deterioration of a quality of image can be prevented, and moreover, each recording operation can be achieved with a high quality.
Another object of the present invention is to provide an ink-jet recording apparatus for practicing an ink-jet recording method of the foregoing type.
A further object of the present invention is to provide an information processing system including an ink-jet recording apparatus of the foregoing type as. outputting means.
In a first aspect of the present invention, there is provided an ink-jet recording method of forming one pixel by ejecting a plurality of ink droplets onto a recording medium at the substantially same location on the latter using an ink-jet recording head including ejecting means for ejecting ink droplets therefrom, the ejecting of the ink droplets from the ink-jet recording head being performed in response to a plurality of ejection signals fed to the ink-jet recording head, wherein
the plurality of ejection signals are generated in such a manner that at least one of a quantity of energy to be fed to the ejecting means per unit time and a total quantity of energy differs from the other one.
Here, the plurality of ink droplets may be ejected onto the recording medium at the substantially same location on the recording medium, an ejection signal for allowing at least one of a quantity of energy to be fed to the ejecting means per unit time and a total quantity of energy to be maximized is selected from the plurality of ejection signals, and subsequently, it is applied to the ejecting means.
The plurality of ink droplets may be shot onto the recording medium at the substantially same location of the recording medium, a preliminary signal for allowing no ink droplet to be ejected from the ejecting means is applied to the ejecting means.
One pixel may be formed by ejecting the plurality of ink droplets onto the recording medium at the substantially same location on the recording medium, the pixel is formed by the ejection of liquid droplets executed by performing scanning plural times.
The ejecting method may be an electrothermal transducer for generating thermal energy required for allowing a phenomenon of film boiling to appear in ink in order to eject ink therefrom.
In a second aspect of the present invention, there is provided an ink-jet recording apparatus including a carriage for displacing an ink-jet recording head in the main scanning direction while the ink-jet recording head is mounted thereon, the ink-jet recording head including ejecting means for ejecting ink droplets onto a recording medium so as to allow input image information to be recorded on the recording medium, a driving unit for feeding a plurality of ejection signals to the ink-jet recording head when the ink droplets are ejected from the ink- jet recording head and a controlling unit for controlling operations of the carriage, the ink-jet recording head, and the driving unit in order to form one pixel by ejecting a plurality of ink droplets on the recording medium at the substantially same location on the recording medium, in response to the plurality of ejection signals, wherein
the controlling unit serves to generate the plurality of ejection signals in such a manner that at least one of a quantity of energy to be fed to the ejecting means per unit time and a total quantity of energy differs from the other one.
When the plurality of liquid droplets may be shot onto the recording medium at the substantially same location of the recording medium, an ejection signal for allowing at least one of a quantity of energy to be fed to the ejecting means per unit time and a total quantity of energy to be maximized is selected from the plurality of ejection signals, and subsequently, it is applied to the ejecting means.
Before the plurality of ink droplets may be shot onto the recording medium at the substantially same location on the recording medium, a preliminary signal for allowing no ink droplet to be ejected from the ejecting means is applied to the ejecting means.
When one pixel may be formed by ejecting the plurality of ink droplets onto the recording medium at the substantially same location on the recording medium, the pixel is formed by the ejection of liquid droplets executed by performing scanning plural times.
The ejecting means may be an electrothermal transducer for generating thermal energy required for allowing a phenomenon of film boiling to appear in ink in order to eject ink therefrom.
The apparatus may be utilized as a printer serving as an output terminal unit for a copying machine, a facsimile, an electronic typewriter, a word processor, a work station and so forth or a handy or portable printer to be equipped in a personal computer, a host computer, an optical disc unit, a video unit and so forth.
In a third aspect of the present invention, there is provided an information processing system including an ink-jet recording apparatus as outputting means, the ink-jet recording apparatus including a carriage for displacing an ink-jet recording head in the main scanning direction while the ink-jet recording head is mounted thereon, the ink-jet recording head including ejecting means for ejecting ink droplets onto a recording medium so as to allow input image information to be recorded on the recording medium, a driving unit for feeding a plurality of ejection signals to the ink-jet recording head when the ink droplets are ejected from the ink-jet recording head, and a controlling unit for controlling operations of the carriage, the ink-jet recording head and the driving unit in order to form one pixel by ejecting a plurality of ink droplets onto the recording medium at the substantially same location on the recording medium, in response to the plurality of ejection signals, wherein
the controlling unit serves to generate the plurality of ejection signals in such a manner that at least one of a quantity of energy to be fed to the ejecting means per unit time and a total quantity of energy differs from the other one.
When the plurality of liquid droplets may be shot onto the recording medium at the substantially same location of the recording medium, an ejection signal for allowing at least one of a quantity of energy to be fed to the ejecting means per unit time and a total quantity of energy to be maximized is selected from the plurality of ejection signals, and subsequently, it is applied to the ejecting means.
Before the plurality of ink droplets may be shot onto the recording medium at the substantially same location on the recording medium, a preliminary signal for allowing no ink droplet to be ejected from the ejecting means is applied to the ejecting means.
When one pixel may be formed by ejecting the plurality of ink droplets onto the recording medium at the substantially same location on the recording medium, the pixel is formed by the ejection of liquid droplets executed by performing scanning plural times.
The ejecting means may be an electrothermal transducer for generating thermal energy required for allowing a phenomenon of film boiling to appear in ink in order to eject ink therefrom.
The information processing system may be an information processing system which is selected from a group consisting of a copying machine, a facsimile, an electronic typewriter, a word processor, a work station, a personal computer, a host computer, an optical disc unit and a video unit.
The above and other objects, effects, features and advantages of the present invention will become apparent from reading of the following description on preferred embodiments thereof in conjunction with the accompanying drawings.